Boston on high alert following marathon explosions

Massachusetts Gov. Deval Patrick pauses as he speaks about the explosions during a newsess conference as Boston Boston Police Commissioner Edward Davis, left, looks on, Monday, April 15, 2013, in Boston. Two explosions shattered the finish of the Boston Marathon, sending authorities out on the course to carry away the injured while stragglers in the 26.2-mile race were rerouted away from the smoking site.

In a press conference, Boston Police Commissioner Ed Davis asked the people in Boston to stay home and for those who are at hotels in the area to stay in their rooms. "We want to make sure we completely stabilize this," he said. Additionally, Massachusetts Gov. Deval Patrick asked people to stay out of crowds and calmly make their way home.

On Twitter, the Boston Police Department said that people should expect to see a high presence of police visibility at key locations, and that the "area around crime scene will be closed for the foreseeable future."

Meanwhile, the Federal Aviation Administration created a no-fly zone over the site of the two explosions and briefly ordered flights bound for Boston's Logan International Airport held on the ground at airports around the country.

About an hour after the explosions the FAA issued a notice to pilots that a no-fly zone with a 3.5-mile radius has been created over 811 Boylston Street. The zone was later reduced in a subsequent notice to a 2.3-mile radius. The zone is limited to flights under 3,000 feet in altitude, which is lower than most airliners would fly except when taking off or landing.

The no-fly zone was effective immediately, and will remain in effect until further notice, the agency said. Pilots planning flights are urged to call their local flight service station.

In order to prevent planes from violating the no-fly zone, the FAA briefly held planes bound for Logan around the country on the ground while air traffic procedures at the airport were reconfigured to bring planes in from the northeast and send them out to the southeast over Boston harbor.

Security for outbound international flights has been stepped up in the wake of the bombings, federal law enforcement officials said. Numerous runners were expected to leave Boston after race, and the additional security has been added as a precaution, they said. The officials requested anonymity

Cellphone companies say service is operating in the Boston area, but with heavy traffic following the explosions. A law enforcement official, citing an intelligence briefing, said cellphone service had been shut down Monday in the Boston area to prevent any potential remote detonations of explosives.

But officials with Verizon Wireless and Sprint Nextel said there had been no such requests.Sprint spokeswoman Crystal Davis said: "Minus some mild call blocking on our Boston network due to increased traffic, our service is operating normally."

On its Web site, the Massachusetts Bay Transportation Authority announced that it is ending service on the Green Line between Kenmore and Park Street Stations, while also temporarily suspending B and C-line service. Meanwhile, its Orange and Red Line service will pass the Downtown Crossing Station.

As of Monday afternoon, Amtrak announced that its trains are operating as scheduled.

The Brigham and Women's Hospital is in lockdown and no one is permitted to enter except hospital staff and patients, CBS Boston reported. Also, the Boston Police Department had evacuated Tufts Medical Center's emergency department as a precaution. The medical center clarified in a tweet that no explosion occurred there, that it was a suspicious item that was located, and that its emergency department is back to normal.